The present invention relates to a photomultiplier. More particularly, the invention relates to a photomultiplier used in liquid scintillation counting. The photomultiplier has an envelope, a base, an anode, a dynode structure and a photocathode and the specimen is placed in a measuring area of the envelope for scintillation counting.
Two different designs are in principle currently used for the shape of the photocathode of a photomultiplier. The first design utilizes a thin, convex window. The convexity of the cathode surface is a disadvantage of this design.
The second design known in the art utilizes a thick, straight photowindow; that is, the surface of the photocathode is planar. The disadvantage of this design is that comparatively thick glass must be used therein.